Mail production systems such as those applicable for use with the present invention, are typically used by organizations such as banks, insurance companies and utility companies for producing a large volume of specific mailings where the contents of each mail item are directed to a particular addressee. Also, other organizations, such as direct mailers, use inserts for producing a large volume of generic mailings where the contents of each mail item for each addressee are substantially identical.
A typical inserter system for producing mail will, in some respects, resemble a manufacturing assembly line. Sheets and other raw materials (e.g. enclosures, and envelopes) enter the inserter system as inputs. Then, a plurality of different modules or workstations in the inserter system work cooperatively to process the sheets until a finished mail piece is produced. The exact configuration of each inserter system depends upon the needs of each particular installation or customer.
Normally, inserter systems prepare mail pieces by gathering collations of documents on a conveyor. The collations are then transported on the conveyor to an insertion station where they are automatically stuffed into envelopes. After being stuffed with the collations, the envelopes are removed from the insertion station for further processing. Such further processing may include automated closing and sealing the envelope flap, weighing the envelope, applying postage to the envelope, and finally sorting and stacking the mail pieces.
Mail processing machines are often required to process up to 22,000 pieces of mail an hour. Such a high processing speed may require envelopes in an output subsystem to have a velocity in a range of 100-120 inches per second (ips) for processing. Postage meters are time sensitive components of a mail processing system, and they must print a clear postal indicia on the appropriate part of the envelope to meet postal regulations.
Older techniques for printing on envelopes in a mail production process involve mechanical print technology, such as a mechanical print head that comes into contact with the envelope. However, digital printing, such as thermal inkjet technology, is increasingly used, as described in Sussmeier (U.S. Pat. No. 6,783,290), according to which a mail piece is decelerated for printing, and then accelerated when the printing is done; this Sussmeier patent is fully incorporated herein by reference.
Facing identification mark (FIMs), indicias, and text are often printed with distortion, because of varying displacements between the print nozzle plane and points within the print image space. These distorted images can negatively affect machine and human read rates.
FIMs and indicias printed on envelopes to USPS specification are typically located very close to the edge of an envelope. For mail of significant thickness, the edges of the envelope are curved rather than flat, and so the ink droplet must travel farther before reaching the paper for points nearer to the edge. As envelope velocities get higher, the ink drop will be more displaced from its intended target position, thus causing greater image distortion. With increased paper velocity, image distortion increases, resulting in higher likelihood of encountering machine readability problems.
Stepped mail introduces a similar problem. Stepped mail involves thick inserts like compact discs (CDs), credit cards, or other discs (e.g. DVDs). These inserts can be located fully or partially under the printed image space, either due to shifting within the envelope, or due to fixed positioning within the envelope. Again, this produces irregularities on the envelope surface, and consequent image distortion due to variations in ink drop time.
Of course, it would theoretically be possible to print on the envelopes before material is inserted into the envelopes. However, this type of approach can be disadvantageous for various reasons. For example, there could be integration problems with existing mail processing equipment which already print after stuffing. Another example is if a stuffing error causes an envelope to be discarded, it would be simpler to discard an envelope that has not yet been printed, and so there would be no need for reprinting FIMs, indicia, or text.
In U.S. Pat. No. 6,796,628, titled Contour Correcting Printer, and assigned to the assignee of the present invention, a printer is described that is suitable for printing on contoured surfaces. That patent is hereby incorporated by reference in its entirety. In a mail production environment, however, there is a need to print on variably contoured mail piece surfaces quickly, and without complicated measurements being done on the mail piece. Accordingly, the printer described in the prior patent may not be suitable by itself for use with mail production systems discussed above.